Striking face of a golf club head

ABSTRACT

Manufacturing methods for manufacturing a striking face of a golf club head. An example method includes: cutting a near-beta titanium alloy into a pre-forged face insert; providing the pre-forged face insert into a heating apparatus for a duration of less than 10 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; forging the heated, pre-forged face insert to form a forged face insert; and attaching the forged face insert to a body of the golf club head to form the striking face of the golf club head.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patent application Ser. No. 17/204,042, filed on Mar. 17, 2021, which claims the benefit of and priority to U.S. Provisional Application No. 63/006,786, filed on Apr. 8, 2020, and U.S. Provisional Application No. 63/052,670, filed Jul. 16, 2020, the disclosures of which are all incorporated by reference in their entirety. To the extent appropriate, priority is claimed to each of the applications.

FIELD OF THE INVENTION

The present invention relates generally to an improved striking face of a golf club head. More specifically, the present invention relates to a striking face having one or more thickened central region located near one or more “region of excessive performance” on the striking face, a thinned perimeter portion located around a perimeter of the striking face, and a transition region that transitions from each of the one or more thickened central region towards the thinned perimeter portion.

BACKGROUND OF THE INVENTION

The game of golf, just like any other sport, has been dominated by professional athletes that are so good at their craft, they almost defy what we often perceive to be the limits of human performance. Take for example the game of basketball, it has been rumored that the height of the basket being set at 10 feet by Dr. James Naismith because he thought that is the height where no human could possibly dunk a basketball. Despite the fact that dunking of the basketball is now a common occurrence, the game of basketball remains largely unchanged despite the increased performance of the athletes achieving feats that were previously unimaginable.

Another illustration of professional athletes achieving amazing feats through time can be seen by one of the most basic measurements of athletic performance in the 100 meters dash. Currently, the world record holder of the 100 meters dash, and generally considered the fastest man in the world is Usain Bolt at 9.58 seconds in 2009. Just merely 10 years before that, the world record for the 100 meters dash was 9.79 seconds by Maurice Greene in 1999. Finally, not too many years ago, Carl Lewis set the world record for the 100 meters dash at 9.93 seconds back in 1987. And looking way back through time, Bob Hayes set the world record at a time of 10.06 seconds back in 1964.

The game of golf, on the other hand, has had a very different path towards todays modern game. The game of golf, ruled by the governing bodies, has been limiting the performance of the athlete by limiting the performance of the equipment used to play the game. The governing bodies of golf have instilled numerous limits on the performance of the game by limiting the size and weight of the golf ball, the Coefficient of Restitution (COR) of the golf ball, the size and volume of the golf club, the COR of the golf club (and indirectly via a USGA created Contact Time [CT]) test, and limitations on Moment of Inertia (MOI) of the golf club head, as well as most recently limitations on scoreline dimensions. All these limitations serve the purpose of limiting the performance of the golf equipment, and indirectly limiting the performance of the game itself.

In order to comply with these requirements, golf club designers have attempted to design golf clubs within the parameters of the governing bodies. In one early example, U.S. Pat. No. 8,221,260 to Stites et al. shows a wood-type golf club head that includes a body, heel, toe, crown, sole, and weighted rear portion; having a moment of inertia about a vertical axis passing through the club center of gravity of at least 5,000 g-cm². This patent attempts to design a golf club that is in conformance with the USGA's limitation on the maximum moment of inertia without exceeding the limitation.

U.S. Pat. No. 7,331,877 to Yamaguchi et al. provides an example of a golf club having a maximum resilience point of a head positioned above a center of a hitting surface in accordance with a pendulum test determined by the USGA has a maximum volume. This patent attempts to design a golf club that is in conformance with the USGA's limitation on CT as well as the volume requirements.

FIGS. 15a and 15b of the accompanying drawings shows the analysis of two striking face portions of two prior art golf club heads in accordance with the existing approach to striking face design. FIG. 15a shows the results of the analysis of a conventional striking face portion of a golf club head having a variable face thickness profile. Although there may be a lot of numbers on the page, this chart has been normalized with the limit of excessive performance set at zero. Hence, a closer examination of this chart will reveal that there are regions on the left and right side of the chart that have numbers that exceed this limit of excessive performance, rendering this design not only less than optimal, but potentially be deemed non-confirming by the governing bodies of golf. FIG. 15b shows the existing methodology to address issues with regions of excessive performance is to just thicken portions of the face that contain the excessive performance, but this methodology also adversely affects the performance of the golf club head across the entire face as shown in FIG. 15b , rendering this solution less than desirable.

Hence, based on the above, there exists a need to be constantly improving upon the performance of a golf club head all while staying in the confines of the rules provided by the game's governing bodies.

BRIEF SUMMARY OF THE INVENTION

In an aspect, the technology relates to a method for manufacturing a striking face of a golf club head. The method includes cutting a near-beta titanium alloy into a pre-forged face insert; providing the pre-forged face insert into a heating apparatus for a duration of less than 10 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; forging the heated, pre-forged face insert to form a forged face insert; and attaching the forged face insert to a body of the golf club head to form the striking face of the golf club head.

In an example, the pre-forged face insert has a thickness (T), and the forging causes a significant deformation to be formed in the forged face insert, the significant deformation including a protrusion having a depth (D) that is at least 25% of the thickness (T) of the pre-forged face insert. In another example, the protrusion depth (D) is less than 50% of the thickness (T) of the pre-forged insert. In a further example, the duration is between 6-8 minutes. In still another example, the titanium alloy has a molybdenum equivalency (MoE) of about 8 to about 10. In yet another example, the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as:

${\frac{\begin{pmatrix} {{{UTS}{of}{striking}{face}{portion}} -} \\ {{UTS}{of}{body}{portion}} \end{pmatrix}}{\begin{pmatrix} {{{Hardness}{of}{striking}{face}{portion}} -} \\ {{Hardness}{of}{body}{portion}} \end{pmatrix}} = {{Strength}{over}{Hardness}{Ratio}}},$

where UTS is Ultimate Tensile Strength. In a further example, the golf club head has a Strength over Hardness Ratio of greater than about 11 ksi/HRC. In another example, the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as:

$\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$

In a further example, the golf club head has a MOR Ratio of greater than about 1.35.

In another aspect, the technology relates to a method for manufacturing a striking face of a golf club head. The method includes cutting a titanium alloy into a pre-forged face insert, the titanium alloy has a molybdenum equivalency (MoE) of about 6 to about 10; providing the pre-forged face insert into a heating apparatus for a duration of less than 10 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; raw forging the heated, pre-forged face insert to form a raw-forged face insert; providing the raw-forged face insert into the heating apparatus for a duration of less than 10 minutes; heating the raw-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; detail forging the heated, raw forged face insert to form a detail-forged face insert; and attaching the attaching the detail-forged face insert to a body of the golf club head to form the striking face of the golf club head.

In an example, the titanium alloy has a molybdenum equivalency (MoE) of about 8 to about 10. In another example, the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as:

${\frac{\begin{pmatrix} {{{UTS}{of}{striking}{face}{portion}} -} \\ {{UTS}{of}{body}{portion}} \end{pmatrix}}{\begin{pmatrix} {{{Hardness}{of}{striking}{face}{portion}} -} \\ {{Hardness}{of}{body}{portion}} \end{pmatrix}} = {{Strength}{over}{Hardness}{Ratio}}},$

where UTS is Ultimate Tensile Strength. In a further example, the golf club head has a Strength over Hardness Ratio of greater than about 11 ksi/HRC. In still another example, the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as:

$\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$

In a further example, the golf club head has a MOR Ratio of greater than about 1.35.

In another aspect, the technology relates to a method of manufacturing a striking face of a golf club head. The method includes cutting a near-beta titanium alloy into a pre-forged face insert having a thickness (T); providing the pre-forged face insert into a heating apparatus for a duration between 6-8 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; forging the heated, pre-forged face insert to form a forged face insert with a significant deformation, the significant deformation including a protrusion having a depth (D) that is at least 25% of the thickness (T) of the pre-forged face insert; and attaching the forged face insert to a body of the golf club head to form the striking face of the golf club head.

In an example, the near-beta titanium alloy has a molybdenum equivalency (MoE) of about 8 to about 10. In another example, the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as:

${\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}} -} \right. \\ {\left. {{UTS}{}{of}{body}{portion}} \right)} \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}} -} \right. \\ \left. {{Hardness}{of}{body}{portion}} \right) \end{matrix}} = {{Strength}{over}{Hardness}{Ratio}}},$

where UTS is Ultimate Tensile Strength. In a further example, the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as:

$\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$

In still another example, the protrusion depth (D) is less than 50% of the thickness (T) of the pre-forged insert.

One aspect of the present invention is a golf club head comprising of a striking face portion having a circumference defined by a striking face perimeter shape, located at a frontal portion of the golf club head; and a aft body portion located rearward of the striking face portion, at a rear portion of the golf club head. The striking face portion further comprises a first region of excessive performance defining a first perimeter shape, and a first layer of increased thickness located at an internal surface of the striking face portion, the first layer of increased thickness having a circumference defined by the first perimeter shape, and a second region of excessive performance defining a second perimeter shape and a second layer of increased thickness located at an internal surface of the first layer of increased thickness, the second layer of increased thickness having a circumference defined by the second perimeter shape. The striking face perimeter shape is different from the first perimeter shape, the second perimeter shape is different from the first perimeter shape, and the second perimeter shape is different from the striking face perimeter shape, and wherein the transition region between the striking face portion, the first layer of increased thickness, and the second layer of increased thickness consists of a smooth blend.

In another aspect of the present invention is a golf club head comprising of a striking face portion, having a circumference defined by a striking face perimeter shape, located at a frontal portion of the golf club head, and an aft body portion located rearward of the striking face portion, at a rear portion of the golf club head. The striking face portion further comprises a thickened central region having a first thickness, a transition region having a second thickness, and a thinned perimeter region having a third thickness, wherein the first thickness is greater than the second thickness, and the second thickness is greater than the third thickness. The striking face portion exhibits a CT Variance Average closer to zero than about −3.5, the CT Variance average defined by the equation

CT Variance Average=Average of CT Values within centered 6 mm Square.

In another aspect of the present invention is a method of determining a rear contour of a golf club striking face comprising the steps of, providing a striking face portion having a substantially uniform thickness, analyzing the striking face portion for a performance value across the striking face portion, identifying one or more regions of excessive performance, identifying one or more first perimeter shape of the first region of excessive performance. Subsequently adding a one or more first layers of increased thickness having a circumference defined by the first perimeter shape and re-analyzing the striking face portion containing the one or more first layers of increased thickness for a performance value across the striking face portion, re-identifying a one or more second regions of excessive performance, re-identifying a one or more second perimeter shape of the second region of excessive performance. Subsequently adding in one or more second layer of increased thickness having a circumference defined by the second perimeter shape, and smoothing out the transition between the striking face portion, the first layer of increased thickness, and the second layer of increased thickness to create a smooth blend.

In another aspect of the invention is a golf club head having a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, said Strength to Hardness Ratio defined as;

$\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}{}102} -} \right. \\ \left. {{UTS}{of}{body}{portion}104} \right) \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}102} -} \right. \\ \left. {{Hardness}{of}{body}{portion}{}104} \right) \end{matrix}} = {{Strength}{over}{Hardness}{{Ratio}.}}$

In another aspect of the invention, is a golf club head having a MOR Ratio of greater than about 1.25, said MOR Ratio defined as;

$\frac{{MOR}{of}{striking}{face}{portion}102}{{MOR}{of}{body}{portion}{}104} = {{MOR}{{Ratio}.}}$

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.

FIG. 1 of the accompanying drawings shows a perspective view of a golf club head in accordance with an exemplary embodiment of the present invention;

FIG. 2 of the accompanying drawings shows a frontal view of a golf club head in accordance with an exemplary embodiment of the present invention;

FIG. 3 of the accompanying drawings shows a cross-sectional view of a golf club head in accordance with an exemplary embodiment of the present invention taken along cross-sectional line 3-3′ shown in FIG. 2;

FIG. 4 of the accompanying drawings shows a cross-sectional view of a golf club head in accordance with an exemplary embodiment of the present invention taken along cross-sectional line 4-4′ shown in FIG. 4;

FIG. 5a of the accompanying drawings shows a cut apart rear view of a striking face portion that is used in the methodology to design a golf club head in accordance with the present invention;

FIG. 5b of the accompanying drawings shows the results of the analysis of the striking face portion shown in FIG. 5a for regions of excessive performance;

FIG. 6a of the accompanying drawings shows a cut apart rear view of a striking face portion modifying the striking face portion shown in FIG. 5a to address regions of excessive performance identified in FIG. 5 b;

FIG. 6b of the accompanying drawings shows the results of the analysis of the striking face portion shown in FIG. 6a for regions of excessive performance;

FIG. 7a of the accompanying drawings shows a cut apart rear view of a striking face portion modifying the striking face portion shown in FIG. 6a to address regions of excessive performance identified in FIG. 6 b;

FIG. 7b of the accompanying drawings shows the results of the analysis of the striking face portion shown in FIG. 7a for regions of excessive performance;

FIG. 8a of the accompanying drawings shows a cut apart rear view of a striking face portion modifying the striking face portion shown in FIG. 7a to address regions of excessive performance identified in FIG. 7 b;

FIG. 8b of the accompanying drawings shows the results of the analysis of the striking face portion shown in FIG. 8a for regions of excessive performance;

FIG. 9 of the accompanying drawings shows a cut apart rear view of a striking face portion in accordance with an exemplary embodiment that contains smoothened the transition between the various layers;

FIG. 10 of the accompanying drawings shows a cut apart rear view of a striking face portion in accordance with an alternative embodiment of the present invention;

FIG. 11 of the accompanying drawings shows a cut apart rear view of a striking face portion in accordance with an alternative embodiment of the present invention;

FIG. 12 of the accompanying drawings shows a cut apart rear view of a striking face portion in accordance with an alternative embodiment of the present invention;

FIG. 13 of the accompanying drawings shows a cut apart rear view of a striking face portion in accordance with an alternative embodiment of the present invention;

FIG. 14 of the accompanying drawings shows a cut apart rear view of a striking fee portion in accordance with an alternative embodiment of the present invention;

FIG. 15a of the accompanying drawings shows a chart analyzing the performance of the striking face portion of a prior art golf club head;

FIG. 15b of the accompanying drawings shows a chart analyzing the performance of the striking face portion of another prior art golf club head; and

FIG. 15c of the accompanying drawings shows a chart analyzing the performance of a striking face portion in accordance with the present invention.

FIG. 16 depicts an example method for manufacturing a striking face of a golf club head.

FIG. 17 depicts another example method for manufacturing a striking face of a golf club head.

FIGS. 18A-C depict an example face insert at different phases of the manufacturing process.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description describes the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Various inventive features are described below and each can be used independently of one another or in combination with other features. However, any single inventive feature may not address any or all of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below.

FIG. 1 of the accompanying drawings shows a perspective view of a golf club head 100 in accordance with an exemplary embodiment of the present invention. In this exemplary embodiment of the present invention, the golf club head 100 may be separated into a striking face portion 102 further comprising a face insert 103, and an aft body portion 104. It should be noted here that the “separation” between the striking face portion 102 and the aft body portion 104 may not contain any physically identifying traits, but rather the striking face portion 102 and the aft body portion 104 are defined more by the criteria described below. The striking face portion 102 may generally refer to the frontal portion of the golf club head 100 having a substantially flat surface (bulge and roll may create slight curvature that is considered to be substantially flat for the purpose of this discussion), whereas the aft body portion 104 refers to any portion of the golf club head 100 rearward of the striking face portion 102.

It should be noted here that one of the most interesting components of the present invention is the face insert 103 itself, especially compared to the remainder of the aft body portion 104. In order to achieve the unique geometry of the various striking face portions 102 to be shown in more detail below, the face insert 103 itself may generally be made out of a titanium material having unique properties.

The face insert 103 of the golf club head 100, in accordance with this exemplary embodiment of the present invention, may generally be made out of a titanium material having a high strength. Although ATI 425® is the preferred material in this embodiment of the present invention, other high strength titanium such as Ti-17, TIMET 54, Ti-9, TIMET 639, VL-Ti, KS ELF, SP-700 could all be used without departing from the scope and content of the present invention as long as it has high strength values to be discussed below. High strength values, as referred to in this invention may generally refer to the Ultimate Tensile Strength (UTS) of the material instead of the yield strength, as elastic deformation in the striking face portion 102 is often desirable to create more performance. However, it should be noted that in alternative embodiments of the present invention, the yield strength of the material most also be considered as well. Moreover, before a discussion on the numbers of the UTS of the striking face material can be had, one should recognize the important difference in the UTS of a material in its natural mill annealed state as compared to when it has been processed to it forming condition. Unless specified otherwise, when referring to UTS, it refer specifically to the UTS in a forming condition, as that is the condition relevant to the actual performance of the golf club head 100 when it is used in the striking face portion 102.

Now that some potential ambiguities have been addressed, we can move on to addressing the actual strength values of the material used for the face insert 103. The face insert 103 of the striking face portion 102 of the golf club head 100, in accordance with this preferred embodiment of the present invention, may have a UTS in a forming condition of greater than about 140 ksi, more preferably greater than about 145 ksi, and most preferably greater than about 150 ksi. Although less relevant to the present invention, it is still worth noting that the UTS of the face insert 103 material in its mill annealed state may generally be greater than about 150 ksi, more preferably greater than about 155 ksi, and most preferably greater than about 158 ksi.

In addition to the UTS of the face insert 103 discussed above, another important characteristic of this high strength material is its relatively low hardness. Once again, hardness of a material differs in its natural mill annealed state as compared to when it has been processed to its forming condition. Similar to above, we are interested in the material when it is in it forming condition. The strength of the face insert 103, in its forming condition, may generally be less than 40 HRC, more preferably less than about 38 HRC, and most preferably less than about 36 HRC. Although less relevant to the present invention, it is still worth nothing that the UTS of the face insert 103 material in its mill annealed state may generally be less than about 41 HRC, more preferably less than about 39 HRC, and most preferably less than about 37 HRC.

Finally, another important characteristic of the material used for the face insert 103 of the striking face portion 102 is its Modulus of Resilience (MOR). MOR is defined by Equation (1) below:

$\begin{matrix} {{MOR} = \frac{{Yield}{Strength}^{2}}{2\left( {{{Young}'}s{Modulus}} \right)}} & {{Eq}.(1)} \end{matrix}$

Once again, because the face material goes through so much transformation to go from its natural mill annealed state as compared to when it is in its final forming condition, the focus here will once again be on the forming condition that replicated the actual performance of the material in a golf club head 100. The face insert 103 material, in its forming condition, may generally exhibit a MOR of greater than about 3.50 MPa, more preferably greater than about 3.75 MPa, and most preferably greater than about 4.0 MPa. Although less relevant to the present invention, it is still worth noting that the MOR of the face insert 103 material in its mill annealed state may generally be greater than about 4.0 MPa, more preferably greater than about 4.25 MPa, and most preferably greater than about 4.5 MPa.

It is critical to recognize here that although the inherent properties of the stronger material used for the face insert 103 of the striking face portion is an important component to achieving the performance of the present golf club head, it is its relative UTS, hardness, and MOR compared to the material used for the body portion that creates the performance benefit of the present invention. Although both the face insert 103 of the striking face portion 102 and the aft body portion 104 are both made out of titanium, the relative difference between the components allows the two components to function together synergistically to create the improvement in performance for the present invention. Hence, in order to establish the baseline material properties for the body portion, we need to first identify one such material that is common to form the aft body portion 104 of the golf club head 100. Although numerous materials such as Ti-8Al-1V-1Mo, Ti-6-4, Ti-5Al-1Sn-1Zr-1V-0.8Mo, Ti-3Al-2.5Sn, and Ti-3Al-2V may be selected, the present preferred embodiment of the present invention utilizes a Ti-8Al-1V-1Mo type material for the chassis. However, all of the materials listed, together with other types of titanium material may also be used without departing from the scope and content of the present invention so long as they contain the material properties outlined in the following paragraph.

Speaking in generalities, Ti-8Al-1V-1Mo, may generally have a UTS of about 132 ksi, a hardness of about 34.55 HRC, and a MOR of about 2.75 MPa. Because the body portion of the golf club head is generally not heat treated, there is no difference in the material in its natural state when compared to its composition in a golf club head 100. Now that the material properties of the standard material used for the chassis has been identified, we can now revert back to the feature that is critical to achieving the synergistic relationship between the face insert 103 of the striking face portion 102 relative to the aft body portion 104. The golf club head 100 in accordance with the present invention may be quantified as a ratio of the difference in UTS between the striking face portion 102 and the aft body portion 104 divided by the difference in hardness between the striking face portion 102 and the aft body portion 104. Alternatively speaking, it can be said that a golf club head 100 exhibits a Strength over Hardness Ratio of greater than 6.0 ksi/HRC, more preferably greater than 11 ksi/HRC, most preferably greater than 16 ksi/HRC. Strength over Hardness Ratio is defined by Equation (2) below:

$\begin{matrix} {\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}{}102} -} \right. \\ \left. {{UTS}{of}{body}{portion}104} \right) \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}102} -} \right. \\ \left. {{Hardness}{of}{body}{portion}{}104} \right) \end{matrix}} = {{Strength}{of}{Hardness}{Ratio}}} & {{Eq}(2)} \end{matrix}$

The strength over Hardness Ratio described above, although is very capable of capturing the synergistic relationship between the different types of titanium material used for the face insert 103 of the striking face portion 102 and the aft body portion 104, does not take in consideration of the MOR relationship between the face insert 103 of the striking face portion 102 and the aft body portion 104. This relationship creates an MOR ratio, and the current inventive golf club head 100 has a MOR Ratio of greater than about 1.25, more preferably greater than about 1.35, and most preferably greater than about 1.45. MOR Ratio defied by Equation (3) below:

$\begin{matrix} {\frac{{MOR}{of}{striking}{face}{portion}102}{{MOR}{of}{body}{portion}{}104} = {{MOR}{Ratio}}} & {{Eq}.(3)} \end{matrix}$

FIG. 2 of the accompanying drawings shows a frontal view of a golf club head 200 in accordance with an exemplary embodiment of the present invention. The frontal view of the golf club head 200 allows cross-sectional line 3-3′ and 4-4′ to be shown more clearly, to which cross-sectional views of the golf club head 200 can be shown more clearly. Cross-sectional line 3-3′ is a vertical line that is orientated in a crown to sole orientation of the golf club head via a face center 203. Cross-sectional line 4-4′ on the other hand, is orientated in a heel to toe orientation, passing through face center 203. FIGS. 3 and 4 below will provide the actual cross-sectional views of the golf club head 200 illustrating the improved striking face in accordance with the present invention. In addition to providing a reference for the cross-sectional views of the golf club head 200, FIG. 2, of the accompanying drawings shows a coordinate system 201 that will govern any discussion relating to orientation of the golf club head 200 for the remainder of the discussion. The x-axis, for the purpose of this patent, relates to an axis that is pointed in a heel to toe direction, with the positive axis pointed at the heel. The y-axis, for the purpose of this patent, relates to an axis that is pointed in a crown to sole orientation, with the positive axis pointed towards the crown. Finally, the z-axis, for the purpose of this patent, relates to an axis that is pointed front and back orientation, with the positive axis pointing towards the front of the golf club head.

FIG. 3 of the accompanying drawings shows a cross-sectional view of a golf club head 300 in accordance with an exemplary embodiment of the present invention. In this cross-sectional view, we can see that the golf club head has a striking face portion 302 located at a frontal portion of the golf club head 300, and a rear aft body portion 304 located rearward and attached to the striking face portion 302. This cross-sectional helps identify some of the key features of the improved striking face portion 302 further comprising of a thickened central region 306, a transition region 308, and a thinned perimeter region 310; each circumferentially surrounding the previous region. Alternatively speaking, it can be said that the transition region comprises a first region of excessive performance having a boundary similar to that of the transition region 308 and a second region of excessive performance having a boundary similar to that of the thickened central region 306. The details of “regions of excessive performance” will be discussed more in detail in subsequent figures.

In this exemplary embodiment of the present invention, the thickened central region 306 may generally have a thickness d1 of between about 3.2 mm to about 3.8 mm, more preferably between about 3.4 mm to about 3.6 mm, and most preferably about 3.5 mm. The thinned perimeter region 310 in accordance with this embodiment of the present invention may generally have a thickness d2 of about 2.4 mm to about 3.0 mm, more preferably between about 2.6 mm to about 2.8 mm, and most preferably about 2.7 mm. The transition region 308 in this embodiment gradually deceases in thickness from d1 to d2 to complete the transition. Although FIG. 3 only shows the cross-sectional view of the striking face portion 302 in a crown to sole orientation, the same type of transition happens in a heel to toe direction as well, as shown in FIG. 4.

FIG. 4 of the accompanying drawings shows a cross-sectional view of a golf club head 400 taken along cross-sectional line 4-4′ shown in FIG. 2, in accordance with an exemplary embodiment of the present invention. In this cross-sectional view shown in FIG. 4 we can see that the golf club head 400 is still mainly comprised out of a striking face portion 402 located at a frontal portion of the golf club head 400 and an aft body portion 404 located behind the striking face portion 402 at a rear portion of the golf club head 400. The current improved striking face portion 402 exhibits a similar profile in a heel to toe orientation it did in a crown to sole orientation shown in FIG. 3. This golf club head 400 has a thickened central region 406, a transition region 408, and a thinned perimeter region 410. The thickened central region 406 and the thinned perimeter region 410 here have identical thicknesses d1 and d2 outlined in FIG. 3, and those measurements apply here as well.

FIGS. 5a -9 will describe in detail the methodology used to achieve the current inventive improve striking face portion 402 of a golf club head 400 in accordance with the present invention, the details of which will shed more light on the design process. More specifically, FIGS. 5a -9 will illustrate the methodology used to achieve the improved striking face design having a variable face thickness by focusing on a baseline face design and identifying regions of excessive performance two or more times until no more regions of excessive performance remain.

Referring now to FIG. 5a to begin the discussion, we can see that the design process begins with a striking face portion 502 comprising of a striking face insert 503 attached to the central portion of the striking face portion 502. This rear cut apart view of the golf club head 500 (not shown) illustrates the rear of the striking face portion 502 in more detail, and the cut apart view allows the internal surface of the striking face portion 502 to be shown more clearly. The rear surface of the striking face portion shown here allows one to identify in FIG. 5a is the projected face perimeter 512 of the golf striking face portion 502. This projected face perimeter 512 is shown in FIG. 5a is depicted by a thickened and darkened line, and certain portions of the projected face perimeter 512 that are not visible from this view is depicted using dashed lines in the sole hosel portions. The projected face perimeter 512 may have a striking face perimeter shape, and this shape is important in defining the improved striking face in accordance with the present invention. It is worthwhile to note here that the projected face perimeter 512 is a projection of the perimeter of the striking face portion 502 taken at an angle that is perpendicular to the ground plane alone an x-y axis as shown in the coordinate system 201 shown in FIG. 2. Finally, it should also be noted that the projected face perimeter 512 shown here is generally defined as the boundary at where the striking face portion 502 stop being substantially flat at an external front surface of the striking face portion 502, resulting in the perimeter shape illustrated in FIG. 5 a.

Now that the projected striking face perimeter 512 having a striking face perimeter shape has been defined, the method of determining the improved striking face of the golf club head begins with analyzing a striking face portion 502 with a substantially flat rear surface having a thickness of about 2.7 mm that creates a resultant striking face portion 502 with a completely uniform thickness as shown in FIG. 5a . The analysis performed here is a determination of the performance of the striking face portion 502 to determine regions of excessive performance. The determination of performance of the striking face portion 502, as it relates to the golf industry, relates generally a Coefficient of Restitution (COR), a Contact Time (CT), and/or a stress distribution, and either of these numbers can be used in this analysis without departing from the scope and content of the present invention. The performance of the striking face portion 502, whether it be COR, CT or stress distribution, could be simulated performance via a finite element analysis software, actual measurements on a golf club head, or any other method of determining the performance of the striking face portion 502 also without departing from the scope and content of the present invention.

FIG. 5b of the accompanying drawings shows the outcome of the analysis of performance of the striking face portion 502 shown in FIG. 5a . FIG. 5b shows different regions of performance of the striking face portion 502 exhibiting different performance outcomes. The different shades of grey shown here in FIG. 5b depicts the different performance achieved across the face at the distances outlined by the x and y axis labels. The lightest shade of grey depicts regions that have a lower performance, while the darker shades of grey depicts regions that have a higher performance. The first outer region 522 here depicts a region that have the lowest performance on the striking face portion 502 according to the previous determination. The second outer region 524, surrounded by the first outer region 522, generally achieves a higher performance than the first outer region 522. The third outer region 526, surrounded by the second outer region 524, generally achieves a higher performance than the second outer region 524. The fourth outer region 528, surrounded by the third outer region 526, generally achieves a higher performance than the third outer region 526. Finally, the central region 530, surrounded by the fourth outer region 528, generally achieves the highest performance that is even higher than the fourth outer region 528. The region of excessive performance, which is determined by when the performance exceeds a predetermined limit, is the central region 530 in this embodiment.

In the current exemplary embodiment of the present invention, the criteria for determining the region of excessive performance is selected to be any location where the CT exceeds the USGA CT limit of 239 μs. In an alternative embodiment of the present invention, excessive performance can be set at a CT measurement that even includes the tolerance of the USGA CT limit at 257 μs as well if such a design is desired. However, this criteria based on CT may be changed to an even higher number if desired or a lower number if desired, both without departing from the scope and content of the present invention. Moreover, alternative criteria for determining regions of excessive performance such as COR or stress may be used as well and those limits could vary depending on the needs of the designer also without departing from the scope and content of the present invention.

Once the central region 530 is determined to be the region of excessive performance, the perimeter shape of the central region 530 is determined, and that perimeter shape is used determine the perimeter shape of a layer of increased thickness for the next step in the design process. Alternatively speaking, it can be said that once a first region of excessive performance having a first perimeter shape is determined based on the central region 530, a first layer of increased thickness is added to the internal surface of the striking face portion, wherein the first layer of increased thickness has a circumference that is defined by the first perimeter shape.

FIG. 6a of the accompanying drawing shows the next phase of the design process, wherein a first layer of increased thickness 613 is added to the striking face portion 502 of FIG. 5a to create this new striking face portion 602 to address the issue relating to regions of excessive performance with the striking face portion 502 shown previously. In this embodiment of the present invention, the first layer of increased thickness 613 is generally about 0.3 mm thicker than the baseline thickness of the striking face portion 502, meaning the total thickness of this first layer of increased thickness 613 is about 3.0 mm. Viewing FIG. 6a in conjunction with FIG. 5b should affirm the previous discussion that the first layer of increased thickness 613 has a circumference and a first perimeter shape 614 that is identical to that of the perimeter shape of the central region 530 shown in FIG. 5b , as defining by the region of excessive performance. It is worth noting here that FIG. 5b is a face on view, while FIG. 6 is the back view of the face, hence the image correlation here is an 180° flip image of one another.

It is critical to recognize here that the first perimeter shape 614 is completely different from the face perimeter 512 shape (shown in FIG. 5a ), as the region of excessive performance is not directly correlated to the shape of the perimeter region. This is an important feature to recognize, as conventional prior art logic would dictate that the region of excessive performance, especially in a constant thickness plate, would be a direct offset of the face perimeter 512 shape (shown in FIG. 5a ). The present invention, through analysis and testing, has determined that the optimal perimeter shape for the first region of excessive thickness 613, instead of being a direct offset of the perimeter shape, should instead be based off actual analysis of the regions of excessive performance determined based off the analysis protocol described above.

Although conventional wisdom would end the analysis and design of the improved striking face right here, the present invention recognizes that no good design is ever achieved without verifying the results of your improvement. Thus, a further analysis for regions of excessive performance can be conducted on this new striking face portion 602. FIG. 6b of the accompanying drawings shows the outcome of the analysis of striking face portion 602 having the first layer of increased thickness 613 incorporated. As a closer examination of FIG. 6b shows that it has very similar components to what is shown in FIG. 5b , but with different shapes. FIG. 6b shows a first outer region 622 having the lowest performance, a second outer region 624 with slightly higher performance, a third outer region 626 with an even slightly higher performance, a fourth outer region 628 with an even higher performance, and finally a central region 630 having a region of excessive performance. The threshold for determining the region of excessive performance is generally the same threshold as the previous step in the analysis has outlined but could be a higher threshold or a lower threshold all without departing from the scope and content of the present invention.

Similar to the design process outlined above, the circumference and the perimeter shape of the central region 630 that corresponds with the region of excessive performance is captured and used to implement and improve upon striking face portion 602 and a second layer of increased thickness 715 (shown later in FIG. 7a ) is added on top of the first layer of increased thickness 613. The increase in thickness of the second layer of increased thickness 715 compared to the first layer of increased thickness 613 is about 0.3 mm thicker, resulting in a total thickness at this portion of the striking face portion 702 of about 3.3 mm. FIG. 7a of the accompanying drawings shows striking face portion 702 having a second layer of increased thickness 715 having a circumference that has a second perimeter shape 716. Once again, the shape and geometry of the second layer of increased thickness 715 corresponds to the central region 630 identified in the previous analysis conducted on striking face portion 602. Alternatively speaking, it can be said that once a second region of excessive performance having a second perimeter shape is determined based on the central region 630, a second layer of increased thickness is added to the internal surface of the first layer of increased thickness, wherein the second layer of increased thickness has a circumference that is defined by the second perimeter shape.

Once again, it is critical to recognize here that the second perimeter shape 716 is completely different from the face perimeter shape 512 (shown in FIG. 5a ) as well as the first perimeter shape 614, as the region of excessive performance in striking face portion 602 is not directly related to either the face perimeter shape 512 nor the first perimeter 614 shape.

FIG. 7b shows the result of the analysis when the striking face portion 702 containing a first layer of increased thickness 613 and a second layer of increased thickness 715 have both been added onto the striking face portion 702 to address areas of increased performance. As it can be seen in FIG. 7b shows a first outer region 722 having the lowest performance, a second outer region 724 with slightly higher performance, a third outer region 726 with an even slightly higher performance, a fourth outer region 728 with an even higher performance, and finally a central region 730 having a region of excessive performance. It should also be noted that the scale is now different from before, really focusing in on the middle of the striking face. The threshold for determining the region of excessive performance is generally the same threshold as the previous step in the analysis has outlined but could be a higher threshold or a lower threshold all without departing from the scope and content of the present invention.

Because the result of the analysis still yielded a central region 730 of excessive performance, the circumference and the perimeter shape of the central region 730 is captured again and used to implement and improve upon striking face portion 702 and a third layer of increased thickness 817 (shown later in FIG. 8a ) is added on top of the second layer of increased thickness 715. The increase in thickness of the third layer of increased thickness 817 compared to the second layer of increased thickness 715 is about 0.3 mm thicker, resulting in a total thickness at this portion of the striking face portion 702 of about 3.6 mm. FIG. 8a of the accompanying drawings shows a striking face portion 802 having a third layer of increased thickness 817 having a circumference and a third perimeter shape 818. Once again, the shape and geometry of the third layer of increased thickness 817 corresponds to the central region 730 identified in the previous analysis conducted on striking face portion 702. Alternatively speaking, it can be said that once a third region of excessive performance having a third perimeter shape is determined based on the central region 730, a third layer of increased thickness is added to the internal surface of the second layer of increased thickness, wherein the third layer of increased thickness has a circumference that is defined by the third perimeter shape.

It should be noted here that the increase in thickness of the various layers of increased thickness in this embodiment of the present invention is generally about 0.3 mm each layer, building upon a base layer thickness of 2.7 mm and finally achieving a central portion thickness of about 3.6 mm. This is a critical component to the design of the improved striking face in accordance with the present invention. The controlling variable here is not each layer having 0.3 mm thickness building on top of the previous layer, but the consistency in each layer of increased thickness. Hence, the analysis begins with the difference between the base layer thickness and the ultimate central thickness, and then dividing that by the number of layers required to completely eliminate regions of excessive performance. This relationship can be more clearly shown by Equation (4) below:

$\begin{matrix} {{{Thickness}{of}{Each}{Layer}} = \frac{\begin{matrix} \left( {{{Ultimate}{Central}{Thickness}} -} \right. \\ \left. {{Baseline}{Thickness}} \right) \end{matrix}}{{Number}{of}{Layers}}} & {{Eq}.(4)} \end{matrix}$

Slight tweaks could be made to the individual layers to slightly adjust for fluctuations in the design, especially in the final layer of increased thickness if desired without departing from the scope and content of the present invention.

Once again, it is critical to recognize here that that the third perimeter shape 818 is completely different from the face perimeter shape 512 (shown in FIG. 5a ) as well as the first perimeter 614 shape and the second perimeter 716 shape, as the region of excessive performance in striking face portion 702 is not directly related to either the face perimeter shape 512, the first perimeter shape 614, nor the second perimeter shape 716.

FIG. 8b of the accompanying drawings shows the final step of the analysis, as no regions of excessive performance can be identified based off the design of the striking face portion 802 shown in FIG. 8a . FIG. 8b shows a first outer region 822 having the lowest performance, a second outer region 824 with slightly higher performance, a third outer region 826 with an even slightly higher performance, a fourth outer region 828 with an even higher performance without any central region that contains excessive performance. Once this analysis is complete, FIG. 9 of the accompanying drawings shows a rear view of a striking face portion 902 that is a result of the process described above.

FIG. 9 of the accompanying drawings shows a rear cut apart view of a striking face portion 902 in accordance with an exemplary embodiment of the present invention. The striking face portion 902 shown here in FIG. 9 stems from and closely resembles the striking face portion 802 shown in FIG. 8a , which has already been described to no longer contain any regions of excessive performance. However, in certain situations, when the stress levels of the striking face portion 802 can get too high, or it makes sense from the ease of manufacturing point of view, it may be beneficial to smooth out the transition between the third layer of increased thickness 817, the second layer of increased thickness 715, the first layer of increased thickness 613, and the perimeter of the striking face portion 802 itself, resulting in what is illustrated in FIG. 9. If stress levels and manufacturing are not an issue, the current inventive improved striking face may look identical to what is shown in FIG. 8a without departing from the scope and content of the present invention.

Although FIG. 9 of the accompanying drawings technically comprises a first layer of increased thickness, a second layer of increased thickness, and a third layer of increased thickness, the smoothing of the transition between the various regions makes them harder to see in this embodiment. Thus, for the sake of simplicity in discussion, the striking face portion 902 shown in FIG. 9 can be more easily explained when labeled as a thickened central region 906, a transition region 908, and a thinned perimeter region 910. These terminologies should sound familiar, as the earlier descriptions of cross-sectional views of the present invention previously in FIGS. 3 and 4 utilize these same terminologies. In fact, it can be said that the rear cut apart view of a golf club head that is shown in the cross-sectional views of golf club heads 300 and 400 shown in FIGS. 3 and 4 respectively would look very similar to what is shown here in FIG. 9.

The thickened central region 906 of the striking face portion 902 may generally have a circumference and geometric shape that still coincides with the third region of excessive performance previously discussed in FIG. 7b . This shape may generally have a width d3 of between about 10 mm to about 15 mm, more preferably between about 11 mm to about 14 mm, and most preferably about 12.5 mm all without departing from the scope and content of the present invention. The thickened central region 906 may generally have a height d4 of between about 7 mm to about 11 mm, more preferably between about 8 mm to about 10 mm, and most preferably about 9 mm.

The transition region 908 may generally have a shape that still coincides with the first region of excessive performance previously discussed in FIG. 5b . This shape, may generally have a width d5 of between about 35 mm to about 40 mm, more preferably between about 36 mm to about 39 mm, and more preferably about 37.5 mm; while having a height d6 of between about 18 mm to about 24 mm, more preferably between about 20 mm to about 22 mm, and most preferably about 21 mm all without departing from the scope and content of the present invention.

Before moving onto the remaining figures discussing different striking face portion profiles in accordance with alternative embodiments of the present invention, it should be noted that the physical designs shown here are not absolute and can change depending on the different chassis of different golf club heads. The focus of the present invention is on the method and the resultant improved striking face that stems from identifying various regions of excessive performance and building on layers of increased thickness to address these regions to create a resulting striking face portion with the most evenly distributed performance across the entire face.

FIG. 10 of the accompanying drawings shows a cut apart view of the rear portion of a striking face portion 1002 in accordance with an alternative embodiment of the present invention. Although the rear view of the striking face portion 1002 looks slightly different than the striking face portion 902 and 802, the same design elements exists. The striking face portion 1002 shown here has a first layer of increased thickness 1013, a second layer of increased thickness 1015, a third layer of increased thickness 1017, a fourth layer of increased thickness 1019, and two fifth layers of increased thickness 1021 a and 1021 b. This alternative embodiment illustrates a couple of key principals previously foreshadowed in the prior discussion that were not specifically illustrated. First and foremost, a closer examination of FIG. 10 shows that there are five layers of increased thickness compared to the three layers described in the previous embodiment. The additional layers may be needed in certain situations to ensure that the striking face portion 1002 no longer contain any regions of excessive performance, in fact the process can be repeated as many times as necessary beyond what is shown in FIG. 10 until regions of excessive performance have been removed. The second key principle is illustrated here by the existence of two fifth layers of increased thickness 1021 a and 1021 b. The existence of two fifth layers of increased thickness 1021 a and 1021 b illustrates that although the regions of excessive performance have generally be a single geometric shape that can be easily captured via one region of excessive thickness having one geometric shape, if two completely isolated regions of excessive performance exists as a result of the analysis, separate and distinct layers of increased thickness can be used without departing from the scope and content of the present invention.

It is worth repeating here that because there are five layers of increased thickness shown here in FIG. 10, if the base layer thickness and the ultimate central thickness layers stayed the same at 2.7 mm and 3.6 mm respectively; each layer of increased thickness will have a thickness of about 0.18 mm on top of its previous base layer in accordance with Equation (1) identified above. However, in alternative embodiments of the present invention, the base layer and the ultimate desired central thickness layer can be different resulting in different thicknesses without departing from the scope and content of the present invention.

FIG. 11 of the accompanying drawings shows a cut open view of the rear of a striking face portion 1102 in accordance with an alternative embodiment of the present invention. FIG. 11 only shows two layers of increased thickness comprising of a first layer of increased thickness 1113 and a second layer of increased thickness 1115. This alternative embodiment of the present invention illustrates another key principal previously foreshadowed but not explicitly shown. More specifically, the striking face portion 1102 shown here may have identified a region of excessive performance that is not substantially centered on the previous layer of increased thickness. This off centered placement of the second layer of increased thickness 1115 on top of the first layer of increased thickness 1113 will not yield a consistent transition region around the entirety of the second layer of increased thickness 1115. A closer examination of the striking face portion 1102 shown in FIG. 11 shows that the placement of the second layer of increased thickness 1115 has a transition portion that blends into the transition of the first layer of increased thickness 1113 near the upper toe portion, illustrating this effect.

FIG. 12 of the accompanying drawings shows a cut open view of a rear of a striking face portion 1202 in accordance with an alternative embodiment of the present invention. In this alternative embodiment, the striking face portion 1202 may have a smoothened transition portion between the various layers of increased thickness similar to what was previously illustrated in FIG. 9. In these smoothened embodiments of the striking face portion, the identifiable features are a thickened central region 1206, a transition region 1208, and a thinned perimeter portion 1210. This embodiment of the present invention illustrates a more elongated central portion 1206 and transition region 1208, which may be the result of the analysis based on this embodiment of the present invention. The thickened central region 1206 may generally have a width d3 of between about 20 mm to about 25 mm, more preferably between about 21 mm to about 24 mm, and most preferably about 22.5 mm all without departing from the scope and content of the present invention. The thickened central region 1206 may generally have a height d4 of between about 7 mm to about 11 mm, more preferably between about 8 mm to about 10 mm, and most preferably about 9 mm.

The transition region 1208 may generally have a width d5 of between about 38 mm to about 48 mm, more preferably between about 39 mm to about 42 mm, and more preferably about 40.5 mm; while having a height d6 of between about 18 mm to about 24 mm, more preferably between about 20 mm to about 22 mm, and most preferably about 21 mm all without departing from the scope and content of the present invention.

FIG. 13 of the accompanying drawings shows a cut open view of a rear of a striking face portion 1302 in accordance with a further alternative embodiment of the present invention. In this alternative embodiment, if the analysis that identifies areas of excessive performance identifies multiple isolated locations across the face, multiple individual layers of increased thickness may be utilized without the need for additional layers of increased thickness on top of the existing regions. The striking face portion 1302 shown here has multiple first layer of increased thickness 1313 a, 1313 b, 1313 c, 1313 d, and 1313 e, corresponding with regions of excessive performance identified in the analysis step. With only one layer of increased thickness, the transition regions all blend out from the central region towards the perimeter in a consistent fashion yielding the geometry shown in FIG. 13. In this embodiment, since there is only one layer of increased thickness, the thicknesses of the multiple layers of increased thickness 1313 a, 1313 b, 1313 c, 1313 d, and 1313 e may have a thickness of closer to 3.6 mm based on Equation (1) above. However, it should be appreciated here that the thicknesses of 1313 a-e may all be different from one another in an even further alternative embodiment of the present invention without departing from the scope and content of the present invention.

FIG. 14 of the accompanying drawings shows a cut open view of a rear of a striking face portion 1402 in accordance with a further alternative embodiment of the present invention. This alternative embodiment is very similar to the striking face portion 1302 shown in FIG. 13, but has only four first layer of increased thickness, 1413 a, 1413 b, 1413 c, and 1413 d. Similar to the previous discussion, in certain situations, when isolated small regions of excessive performance are identified, the resultant design may look like what is shown here in FIGS. 13 and 14 without departing from the scope and content of the present invention.

FIGS. 15a, 15b, and 15c show CT heat maps of two prior art striking face portions as well as the current inventive striking face portion. These CT heat maps are all created replicating a frontal face on view of the striking face, with the left side of the heat map referencing the toe side of the golf club head, the right side referencing the heel side of the golf club head, the top side referencing the crown of the golf club head, and the bottom referencing the sole side of the golf club head. Moreover, before diving into the discussion on the various charts, it should be noted that although there are a lot of numbers on the page, it should be appreciated that all the numbers have been normalized to set the “limit of excessive performance” to be zero. Hence, any number that has a positive value is undesirable because it exceed the limit previously set. Conversely, too large of a negative number is also undesirable, because it means that the limit has not been reached, and there are performance gains that are unachieved. Finally, the axes to the charts denote the distance, in meters, from the center of the striking face where the measurement is obtained. As you can see, the charts all have a measurement in a heel and toe direction that goes from −0.02 meters (20 mm) on the toe side to a positive 0.02 meters (20 mm) on the heel side, in 0.002 meters (2 mm) increments. The charts also have a range of −0.008 meters (8 mm) on the sole side to a positive 0.012 meters (12 mm) on the crown side.

FIG. 15a shows a prior art striking face portion's CT heat map distribution that is less than optimal. One of the key identifiers of good performance is the CT value near the center of the face, identified by the two zeros on the axes has a CT value of −5, with the highest CT value slightly above face center at −1. Although these seem like good performance results initially, a closer examination of the remainder of the face map reveals that there are numerous locations on the heel and toe portion of the face that have numbers in the positive territory. As previous discussions have indicated, having any regions that exceed the performance limit is not only undesirable, but could be deemed to be non-conforming by the governing bodies of golf. In addition to the fatal flaw below, an average performance number around the center of the face (a square created by moving 0.006 meters [6 mm] in all directions heel, toe, crown, and sole, and highlighted in the chart by darkened perimeter) is −5.37. This is such a critical component in determining the performance of the golf club head around face center, it is referred to as a “CT Variance Average” and further defined by Equation (5) below.

CT Variance Average=Average of CT Values within centered 6 mm Square  Eq. (5)

Needless to say, as negative numbers indicate a less than optimal performance, a number closer to 0 is more desirable. Alternatively speaking, it can be said that this prior art golf club head has a CT Variance Average of about −5.37.

FIG. 15b of the accompanying drawings shows the CT heat map of another prior art golf club head wherein an attempt has been made to address the issue of CT exceeding the limit of excessive performance, but the CT Variance Average has suffered. A closer examination of FIG. 15b shows that through efforts to eliminate any regions of having excessive performance, generally achieved by thickening up portions of the striking face that exhibits excessive performance, there are no positive values on the chart. However, the CT Variance Average here suffers, as this design yields a CT Variance Average of −7.00.

FIG. 15c of the accompanying drawings shows a CT heat map of the current inventive golf club head. Right off the bat, it can be seen that this inventive golf club head has no regions of excessive performance with no values in the positive territory. Moreover, the present invention has a really good CT Variance Average of −2.90, meaning its face center performance is much closer to the limit than any of the previous designs. Alternatively speaking, it can be said that the current inventive golf club head has a CT Variance Average of closer to zero than about −3.5, more preferably closer to zero than about −3.2, and more preferably closer to zero than about −3.0.

As discussed above, the face insert (e.g., striking face 103) forming the striking face of the golf club head may generally be made out of a titanium material having a high strength (e.g., various titanium alloys discussed above). To create a face insert with properties and characteristics suitable for a striking face of a golf club head, the face insert may be forged to have a variable thickness and/or may be forged to have a complex curved shape. For instance, the curved shape may be defined at least in part by the bulge and roll of the face insert 103. According to some embodiments, the geometry of the face insert may be forged by a stamped forging process that uses a die assembly. The die assembly may include a top punch or male die that has a protrusion created in roughly the shape of the desired variable face insert geometry (e.g., variable thickness, complex curved shape, etc.). The die assembly may further include a bottom cavity or female die that has a corresponding depression that also corresponds to the desired variable face insert geometry. According to the stamped forging process, the top punch applies pressure onto the face insert to deform the face insert into the desired shape.

During the stamped forging process, some titanium materials may be required to be heated to an elevated temperature where the titanium material becomes more ductile. Exposing metals such as titanium materials to elevated temperatures, however, can lead to loss of strength of the metals. The strength loss of the metals may be exacerbated by increasing the temperature applied to the metals and/or increasing the duration of time that the metals are exposed to elevated temperatures. Generally, an increased temperature may have a stronger detrimental effect than the duration of the heating process.

In the case of titanium alloys, the situation is further complicated because the microstructure of titanium alloys may undergo phase transformation at elevated temperatures. For example, pure titanium may change its crystal structure from a hexagonal-close-packed (HCP) crystal structure to a body-centered-cubic (BCC) crystal structure when heated above a certain temperature (e.g., about 882° C.). The HCP crystal structure may be referred to as the alpha phase while the BCC crystal structure may be referred to as the beta phase. The temperature at which the titanium alloy structure transforms from the alpha phase to the beta phase is referred to as the beta-transus temperature. When a titanium alloy is heated above its beta-transus temperature and maintained above the beta-transus temperature, the titanium alloy may transform from the alpha phase to the beta phase. Also, when the titanium alloy is held above the beta transus-temperature, the size of beta grains within the beta phase structure may increase. The grains may also grow in heterogenous patterns, which may further reduce the strength of the material. When the titanium alloy is cooled, the larger beta grains may create a more coarsely grained microstructure. The coarsely grained microstructure may reduce the strength and/or ductility of the titanium alloy, which effectively makes the resultant titanium alloy less suitable for use as a striking face of a golf club. As such, when forming such a striking face, it is desirable to avoid the formation of such large or coarse beta grains.

Additional elements in a titanium alloy (e.g., alloying elements) can affect the beta-transus temperature of the titanium alloy. For example, alloying elements that favor alpha phase (e.g., alpha-stabilizing elements) raise the beta-transus temperature, while elements that favor the beta phase (e.g., beta-stabilizing elements) lower the beta-transus temperature. Some examples of alpha-stabilizing elements include aluminum (Al) and oxygen (O). Some example beta-stabilizing elements include vanadium (V), iron (Fe), molybdenum (Mo), nickel (Ni), palladium (Pd), niobium (Nb), and chromium (Cr). Accordingly, the beta-transus temperature of a titanium alloy depends on which alloying elements are added and the amounts of the alloying elements.

Given the potential impact of alloying elements, titanium alloys may be classified according to its concentrations of alpha-stabilizing elements and/or beta-stabilizing elements. For example, room temperature titanium alloys may be classified into three main categories: alpha-phase alloys, dual-phase alpha and beta alloys, and beta-phase alloys. The beta-phase alloy categories may be further divided into near-beta titanium alloys, metastable beta titanium alloys, and the stable beta titanium alloys.

A common parameter for classifying a titanium alloy into one of the above categories is the molybdenum equivalency (MoE). The MoE may be calculated using the formula:

MoE = 1.(wt.%Mo)+0.67(wt.%V)+0.44(wt.%W) + 0.28(wt.%Nb) + 0.22(wt.%Ta) + 2.9(wt.%Fe) + 1.6(wt.%Cr) + 1.25(wt.%Ni) + 1.7(wt.%Mn) + 1.7(wt.%Co) − 1.(wt.%Al)

The MoE value calculated by the equation above can be used to classify a titanium alloy. For example, a near-beta titanium alloy may be defined as a titanium alloy with a MoE from about 8 to about 10, a metastable beta titanium alloy may be defined as a titanium alloy with a MoE from about 10 to about 30, and a stable beta titanium alloy may be defined as a titanium alloy with a MoE greater than about 30.

Generally, titanium alloys that are less beta rich (e.g., have a lower MoE value), such as alpha phase alloys, dual-phase and beta alloys, and near beta alloys, are less ductile and may be required to be heated to forge the desired geometry of the face insert. Due to the problems with heating titanium alloys described previously, titanium alloys that are less beta rich are usually avoided when forming a face insert. This can limit the range of titanium alloys that are suitable for manufacturing a face insert with the desired strength properties described herein when the face insert is manufactured using prior techniques. Such a narrower range of titanium materials leaves manufacturers more susceptible to shortages such as supply chain issues. A new method for manufacturing a face insert that allows for the use of a wider range of titanium alloys without sacrificing strength is therefore needed and provided by the technology disclosed herein.

The present technology controls the manufacturing process in a manner to substantially avoid the negative affects of heating and forging titanium alloys, including near-beta titanium alloys. For instance, various embodiments of the present disclosure are directed toward a method for manufacturing the face insert for the golf club head that allows for use a wider range of titanium alloys while maintaining the strength and ductility of the titanium alloys for use in face insert.

FIG. 16 depicts an example method 1600 for manufacturing a striking face of a golf club head. At operation 1602, a titanium alloy is cut into shape of a face insert to form a pre-forged face insert. The titanium alloy may be one of the alloys discussed above. For instance, the titanium alloy may be a near-beta titanium alloy or an alloy that has an MOE equivalency of between 6-10 or 8-10.

The cutting of the of the titanium alloy may be performed via laser cutting or other suitable methods for cutting titanium alloys. For example, the titanium alloy may be formed as a sheet having a substantially equal thickness, and the pre-forged face insert may be cut from the sheet of titanium alloy. FIG. 18A depicts an example side view of the pre-forged face insert 1800 having a thickness (T).

At operation 1604, the pre-forged face insert is provided into a heating apparatus for a duration that may be less than about ten minutes. In some examples, the duration may be between 6-8 minutes or about 7 minutes. By limiting the time that the pre-forged striking face remains in the heating apparatus, long grain growth and other beta transition effects discussed above may be reduced. When the titanium alloy is a near-beta titanium alloy (or similar alloy), such controls over the heating process become particular important to retain the strength and/or ductility characteristics of the titanium alloy during the heating process. The heating apparatus may be a rotary oven or similar type of heating apparatus suitable for heating titanium alloys to the temperatures described herein.

At operation 1606, the heating apparatus heats the pre-forged face insert to a temperature that remains below the beta-transus temperature of the particular titanium alloy that forms the pre-forged face insert. For instance, for near-beta titanium alloy, the pre-forged face insert may be heated to a temperature between about 740° C. and 780° C. In some examples, the pre-forged face insert is heated to a temperature of about 760° C.

Heating the pre-forged face insert to the temperature ranges may be accomplished by setting the heating apparatus to the desired temperature (e.g., 760° C.) and leaving the pre-forged face insert in the heating apparatus until the pre-forged face insert reaches that desired temperature. In other examples, the heating apparatus may be set to a temperature higher than the desired temperature of the face insert (e.g., higher than 760° C.), and the pre-forged face insert may be left in the heating apparatus for a duration that results in the pre-forged face insert reaching the desired temperature. For instance, once the pre-forged face insert reaches the desired temperature, the pre-forged face insert is removed from the heating apparatus. Removing the heated pre-forged face insert may be accomplished automatically or manually, such as through the use of heat-resistant tongs.

By maintaining and limiting the temperature to such ranges, the beta transition of a near-beta titanium alloy is limited or avoided, and the negative effects of such transition discussed above are similarly limited or avoided. Some heating of the pre-forged face insert, however, may generally be required or useful to perform the forging processes discussed herein and used to generate the types of face inserts with the characteristics discussed herein and face inserts having variable face thicknesses. For instance, cold forming a titanium alloy (e.g., forming the titanium alloy at room temperature) requires substantial amounts of force and even at the high levels of force, the types of substantial deformation discussed herein may not even be possible. When the titanium alloy is heated, however, it becomes softer or more ductile, and less force is required to form or deform the titanium alloy during the forging process. The present technology has identified a unique range of 740° C. and 780° C. (or about 760° C.) that increases the ductility of a near-beta titanium alloy to a point that it can be significantly deformed during the forging process while avoiding the negative effects caused by beta transition of the titanium alloy.

At operation 1608, the heated, pre-forged face insert is forged to form a forged face insert. The forging of the face insert may be accomplished through a stamped forging process that uses a male die and a female die, or top punch and bottom cavity. Additional details regarding a stamped forging process are provided in U.S. Patent Publication No. 2013/0303305, which is incorporated herein by reference in its entirety. In some examples, the portions of the forging or die assembly may be heated to not cause rapid cooling of the face insert when contacting the face insert during the forging process. Once the forging process is complete, the forged face insert may be allowed to cool to set the deformations caused by the forging process.

The forging process may result in more minor deformations, such as forming bulge and roll curvatures, as well as more significant deformations, such as the deformations used to form face inserts having variable face thicknesses. An example of a significant deformation is depicted in FIG. 18B. FIG. 18B depicts side view of a forged face insert 1810 after a forging process has been performed. For instance, a top punch or male die may be pressed near the center of the face insert to push material partially through the face insert. The punch or pressing process results in a cavity 1812 and a protrusion 1814 from the forged face insert 1810 as compared to the pre-forged face insert 1800. The protrusion 1814 may be formed by pushing the material from the front of the face insert towards the back/aft of the face insert. The protrusion 1814 has a maximum thickness or depth (D). The cavity 1812 may have substantially the same depth (D).

The deformation of the pre-forged face insert 1800 to form the forged face insert 1810 may be considered a significant deformation. A significant deformation may be considered a deformation where the protrusion depth (D) is at least 25% of the thickness (T) of the pre-forged face insert 1800. In some examples, the protrusion depth (D) may be between about 25%-50% of the thickness (T) of the pre-forged face insert 1800. As a specific example, the thickness (T) of the pre-forged face insert 1800 may be about 4 mm, and the protrusion depth (D) may be about 1-2 mm. A significant deformation may result in a protrusion depth (D) of at least 1 mm, 1.5 mm, or 2 mm.

Once the forged face insert 1810 has been formed, the forged face insert 1810 may undergo additional manufacturing processes before the forged face insert 1810 is attached to the remainder or body of the golf club head to form the striking face. For example, as shown in FIG. 18C, the forged face insert 1820 may be machined to remove material from the front of the forged insert to form a variable thickness striking face 1820. The front of the forged face insert 1810 may be machined down such that the front of the striking face is flush with the bottom of the cavity (or a lower depth). For instance, a thickness of material equal to at least the cavity/protrusion depth (D) may be removed from the front of the forged face insert 1820. The resultant minimum thickness (T_(M)) of the variable thickness face 1820 may be less than or equal to the pre-forged thickness (T) minus the cavity/protrusion depth (D). Other or additional manufacturing steps, such as polishing, sandblasting, etching (e.g., laser etching), may also be performed prior to attaching the forged face to the body of the golf club head.

Returning to FIG. 16, at operation 1610, the forged face insert is attached to the body of the golf club head to form a striking face of the golf club head. The resultant golf club head may have the characteristics and/or properties discussed herein, such as the Modulus of Resilience (MOR) values, Strength over Hardness Ratio values, and/or MOR ratio values discussed above.

FIG. 17 depicts another example method 1700 for manufacturing a striking face of a golf club head. The method 1700 is similar to method 1600 in that a titanium allow is heated and forged. The method 1700, however, includes two heating and forging operations—a first raw-forging operation and a second detail-forging operation.

At operation 1702, a titanium alloy is cut into a pre-forged face insert. At operation 1704, the pre-forged face insert is inserted into a heating apparatus for a duration, and at operation 1706, the pre-forged face insert is heated. Operations 1702-1706 may be substantially similar or the same as operation 1602-1606. For instance, the pre-forged face insert may be heated to a temperature between 740° C. and 780° C. (or about 760° C.) and heated for a duration of about 6-8 minutes (e.g., about 7 minutes).

At operating 1708, the pre-forged face insert is raw forged to form rougher or less-fine features of the face insert. Raw forging the pre-forged face insert results in a raw-forged face insert. For instance, the raw forging may form the significant deformations discussed above. The raw forging process may include the same type of stamped forging process discussed above.

Subsequent to the raw-forging process in operation 1708 is performed, the raw-forged face insert is again heated by providing the raw-forged face insert into the heating apparatus at operation 1710. For example, after the raw-forging process, the raw-forged face insert may have cooled or been allowed to cool. For a subsequent forging process, the raw-forged face insert is reheated. At operation 1712, the raw-forged face insert is reheated to the same or similar temperatures as the first heating operation (e.g., 740° C. and 780° C.) and for a same or similar duration (e.g., about 6-8 minutes or about 7 minutes). For instance, operations 1710-1712 may be substantially similar to operations 1704-1706.

The heated, raw-forged face insert is then detail forged in operation 1714. The detail-forging process may result in smaller deformations than the raw-forging process of operation 1708. For example, different male/female dies may be used in the detail-forging process than in the raw-forging process. Accordingly, the deformations caused by the second forging process (e.g., the detail-forging process) may produce deformations with different geometries than the deformations caused by the first forging process (e.g., the raw-forging process). The detail-forging process results in a detail-forged face insert. Subsequent to the detail-forging process, additional manufacturing processes may be performed on the detail-forged face insert, such as machining, polishing, sand blasting, etching etc.

At operation 1716, the detail forged face insert is attached to the body of the golf club head to form a striking face of the golf club head. The resultant golf club head may have the characteristics and/or properties discussed herein, such as the Modulus of Resilience (MOR) values, Strength over Hardness Ratio values, and/or MOR ratio values discussed above.

Other than in the operating example, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, moment of inertias, center of gravity locations, loft, draft angles, various performance ratios, and others in the aforementioned portions of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear in the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the above specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the present invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. 

What is claimed is:
 1. A method for manufacturing a striking face of a golf club head, the method comprising: cutting a near-beta titanium alloy into a pre-forged face insert; providing the pre-forged face insert into a heating apparatus for a duration of less than 10 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; forging the heated, pre-forged face insert to form a forged face insert; and attaching the forged face insert to a body of the golf club head to form the striking face of the golf club head.
 2. The method of claim 1, wherein the pre-forged face insert has a thickness (T), and the forging causes a significant deformation to be formed in the forged face insert, the significant deformation including a protrusion having a depth (D) that is at least 25% of the thickness (T) of the pre-forged face insert.
 3. The method of claim 2, wherein the protrusion depth (D) is less than 50% of the thickness (T) of the pre-forged insert.
 4. The method of claim 1, wherein the duration is between 6-8 minutes.
 5. The method of claim 1, wherein the titanium alloy has a molybdenum equivalency (MoE) of about 8 to about
 10. 6. The method of claim 1, wherein the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as: ${\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}} -} \right. \\ {\left. {{UTS}{}{of}{body}{portion}} \right)} \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}} -} \right. \\ \left. {{Hardness}{of}{body}{portion}} \right) \end{matrix}} = {{Strength}{over}{Hardness}{Ratio}}},$ where UTS is Ultimate Tensile Strength.
 7. The method of claim 6, wherein the golf club head has a Strength over Hardness Ratio of greater than about 11 ksi/HRC.
 8. The method of claim 1, wherein the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as: $\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$
 9. The method of claim 8, wherein the golf club head has a MOR Ratio of greater than about 1.35.
 10. A method for manufacturing a striking face of a golf club head, the method comprising: cutting a titanium alloy into a pre-forged face insert, the titanium alloy has a molybdenum equivalency (MoE) of about 6 to about 10; providing the pre-forged face insert into a heating apparatus for a duration of less than 10 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; raw forging the heated, pre-forged face insert to form a raw-forged face insert; providing the raw-forged face insert into the heating apparatus for a duration of less than 10 minutes; heating the raw-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; detail forging the heated, raw forged face insert to form a detail-forged face insert; and attaching the attaching the detail-forged face insert to a body of the golf club head to form the striking face of the golf club head.
 11. The method of claim 10, wherein the titanium alloy has a molybdenum equivalency (MoE) of about 8 to about
 10. 12. The method of claim 10, wherein the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as: ${\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}} -} \right. \\ {\left. {{UTS}{}{of}{body}{portion}} \right)} \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}} -} \right. \\ \left. {{Hardness}{of}{body}{portion}} \right) \end{matrix}} = {{Strength}{over}{Hardness}{Ratio}}},$ where UTS is Ultimate Tensile Strength.
 13. The method of claim 12, wherein the golf club head has a Strength over Hardness Ratio of greater than about 11 ksi/HRC.
 14. The method of claim 10, wherein the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as: $\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$
 15. The method of claim 10, wherein the golf club head has a MOR Ratio of greater than about 1.35.
 16. A method of manufacturing a striking face of a golf club head, the method comprising: cutting a near-beta titanium alloy into a pre-forged face insert having a thickness (T); providing the pre-forged face insert into a heating apparatus for a duration between 6-8 minutes; heating the pre-forged face insert to a temperature between about 740° Celsius (° C.) and 780° C.; forging the heated, pre-forged face insert to form a forged face insert with a significant deformation, the significant deformation including a protrusion having a depth (D) that is at least 25% of the thickness (T) of the pre-forged face insert; and attaching the forged face insert to a body of the golf club head to form the striking face of the golf club head.
 17. The method of claim 16, wherein the near-beta titanium alloy has a molybdenum equivalency (MoE) of about 8 to about
 10. 18. The method of claim 16, wherein the golf club head has a Strength over Hardness Ratio of greater than about 6.0 ksi/HRC, wherein the Strength to Hardness Ratio is defined as: ${\frac{\begin{matrix} \left( {{{UTS}{of}{striking}{face}{portion}} -} \right. \\ {\left. {{UTS}{}{of}{body}{portion}} \right)} \end{matrix}}{\begin{matrix} \left( {{{Hardness}{of}{striking}{face}{portion}} -} \right. \\ \left. {{Hardness}{of}{body}{portion}} \right) \end{matrix}} = {{Strength}{over}{Hardness}{Ratio}}},$ where UTS is Ultimate Tensile Strength.
 19. The method of claim 16, wherein the golf club head has a MOR Ratio of greater than about 1.25, the MOR Ratio defined as: $\frac{{MOR}{of}{striking}{face}{portion}}{{MOR}{of}{body}{portion}} = {{MOR}{{Ratio}.}}$
 20. The method of claim 16, wherein the protrusion depth (D) is less than 50% of the thickness (T) of the pre-forged insert. 